Method and apparatus for cooling produce

Abstract

A vacuum cooling system is provided with controls for reliably and consistently controlling the cooling system for a chamber that holds produce provided with a vacuum pump, a refrigeration system, a vent valve, a bleed valve, first, second and third pressure detectors or pressure set points and a programmable logic controller for starting the pump and then automatically operating the refrigeration system in response to operation of the first pressure detector and then momentarily and repeatedly opening the bleed valve in response to operation of the second detector and wherein the third detector detects a pressure above the second level detector and the control system closes the bleed valve in response to operation of the third pressure detector.

We claim: 
     
       1. Apparatus for cooling produce comprising: a chamber adapted to contain the produce to be cooled,   a vacuum means connected to the chamber for pumping air out of the chamber,   a refrigeration system having a cooling heat exchange coil communicating with the interior of the chamber for cooling fluid in the chamber,   a vent valve for admitting air into the chamber,   a bleed valve for admitting air into the chamber at a restricted rate,   a first pressure detector for detecting a first vacuum level in the chamber below atmospheric pressure,   a second pressure detector for detecting a second vacuum level in the chamber below the pressure of the first vacuum level, and   control means for starting the pump and then automatically operating the refrigeration system in response to operation of the first pressure detector and then momentarily and repetitively opening the bleed valve in response to operation of the second detector.   
     
     
       2. The apparatus of claim 1 in which a third pressure detector is provided for detecting a pressure above the second vacuum level and the control system includes means for closing the bleed valve in response to operation of the third pressure detector. 
     
     
       3. The apparatus of claim 2 in which said third pressure detector detects a pressure of about 4.6 mm. 
     
     
       4. The apparatus of claim 1 in which said first pressure detector detects a pressure of about 300 to 15 mm and said second pressure detector detects a pressure of about 4.5 mm. 
     
     
       5. The apparatus of claim 1 characterized further in that the control means includes means for stopping both the refrigeration system and the vacuum means in response to the frequency of operation of the second detector. 
     
     
       6. The apparatus of claim 1 characterized further in that: said chamber includes means for discharging water in said chamber at a location above said produce to cause cool water to flow downwardly over the produce, and   the control means includes means for stopping both the refrigeration system and the vacuum means and venting the chamber in response to the frequency of operation of the second detector.   
     
     
       7. The method of cooling produce comprising: confining the produce to be cooled in a chamber, connecting a vacuum means to the chamber for pumping air out of the chamber,   connecting a refrigeration system to the chamber with a cooling heat exchange coil communicating with the interior of the chamber,   providing a bleed valve and a vent valve for admitting air into the chamber,   detecting a first vacuum level in the chamber below atmospheric pressure,   detecting a second vacuum level in the chamber below the pressure of the first vacuum level, starting the vacuum means, and   then automatically operating the refrigeration system in response to detecting the first vacuum level and then momentarily and repetitively opening the bleed valve in response to detecting the second vacuum level.   
     
     
       8. The method of claim 7 characterized further by the inclusion of the final step of stopping both the refrigeration system and the vacuum means in response to the frequency of operation of the second detector. 
     
     
       9. The method of claim 7 in which said first vacuum level detected is about 15 to 300 mm and said second vacuum level detected is about 4.5 mm. 
     
     
       10. The method of claim 7 characterized further by the inclusion of the steps of: discharging water in said chamber at a location above said produce to cause cool condensed water to flow downwardly over the produce, and   stopping both the refrigeration system and the vacuum means and opening said vent in response to the frequency of operation of the second detector.